This document was developed by the American College of Cardiology Foundation (ACCF) Task Force on Clinical Expert Consensus Documents (ECDs) and cosponsored by the American College of Radiology (ACR), American Heart Association (AHA), North American Society for Cardiovascular Imaging (NASCI), and

ACCF/ACR/AHA/NASCI/SCMR 2010 Expert Consensus Document on Cardiovascular Magnetic Resonance A Report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents

Expert Consensus DocumentACCF/ACR/AHA/NASCI/SCMR 2010 Expert Consensus Document on Cardiovascular Magnetic Resonance: A Report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents

High-resolution phase-contrast magnetic resonance imaging can now assess flow in proximal and distal cerebral arteries. The aim of this study was to describe how total cerebral blood flow (tCBF) is ...

https://journals.sagepub.com/doi/pdf/10.1038/jcbfm.2014.241

Blood Flow Distribution in Cerebral Arteries

Intracranial atherosclerosis, one of the leading causes of ischemic stroke, is associated with an increased risk for recurrent stroke and dementia.1,2 Individuals of Asian, Hispanic, and African American ancestry are especially affected. Recent European studies revealed a much higher prevalence of intracranial lesions than commonly presumed, suggesting that intracranial atherosclerotic disease is potentially the most common cause of ischemic stroke worldwide.1,3 Ischemic strokes are clinically categorized into 5 subtypes based on their underlying cause: large-artery atherosclerotic stenosis, small-artery disease (lacunes), cryptogenic, major-risk-source cardiogenic embolism, and unusual (eg, dissections, arteritis). Most nonlacunar ischemic strokes are thought to be thromboembolic, which presumably also accounts for most cryptogenic strokes. Embolic sources include minor-risk or covert cardiac sources, veins via paradoxical embolism, and nonocclusive atherosclerotic plaques in the aortic arch or cervical or cerebral arteries.4 Besides embolic strokes, 2 other mechanisms have been associated with intracranial atherosclerosis-related strokes, namely hypoperfusion through a stenotic artery causing watershed or border-zone stroke and plaque overgrowth of perforator artery ostia, which is associated with penetrating artery disease and lacunar infarcts and has been related to cryptogenic strokes.5–7 Even mild stenosis of intracranial atherosclerotic arteries (<50%) may therefore be clinically relevant, and high-resolution magnetic resonance imaging studies are needed to identify and determine the degree and location of stenosis in this patient group.5,8 The possibly causal role of nonstenotic plaques in ischemic stroke highlights the need for more insight into the mechanisms and occurrence of intracranial atherosclerosis.

In the 1960s and 1970s, large, descriptive autopsy studies were conducted, providing classic morphological features of intracranial arteries. Despite the importance of intracranial atherosclerosis to stroke and dementia, there is a lack of more recent mechanistic studies. Therefore, we intend to draw attention to this neglected research field by …

Cause and Mechanisms of Intracranial Atherosclerosis

Cerebral hyperperfusion syndrome develops in a small subset of patients following carotid artery surgery (CAS) performed to treat severe carotid artery stenosis. This syndrome has been found to have a close correlation with cerebral hyperperfusion occurring after CAS. The purpose of this study is to investigate whether and how the anatomy of the Circle of Willis (CoW) of the cerebral circulation influences post-CAS cerebral hyperperfusion. A computational model of the cerebral circulation coupled with the global cardiovascular system has been developed to investigate hemodynamic events associated with CAS. Nine topological structures of the CoW were investigated in combination with various distribution patterns of stenosis in the feeding arteries of the cerebral circulation. The occurrence of post-CAS cerebral hyperperfusion was predicted for the CoW structures that have poor collateral pathways between the stenosed cerebral feeding arteries and the remaining normal feeding arteries. The risk and the localization of post-CAS hyperperfusion were determined jointly by the anatomy of the CoW and the distribution pattern of stenosis in the cerebral feeding arteries. The presence of basilar artery stenosis or contralateral ICA stenosis increased the risk of post-CAS hyperperfusion and enlarged the cerebral region affected by hyperperfusion. For a certain CoW structure, the diameters of the cerebral communicating arteries and the severity of carotid artery stenosis both had a significant influence on the computed post-CAS cerebral hyperperfusion rates. Moreover, post-CAS cerebral hyperperfusion was predicted to be accompanied with an excessively high capillary transmural pressure. This study demonstrated the importance of considering the anatomy of the CoW in assessing the risk of post-CAS cerebral hyperperfusion. Particularly, since the anatomy of the CoW and the distribution pattern of stenosis in the cerebral feeding arteries jointly determine the risk and localization of post-CAS cerebral hyperperfusion, a patient-specific hemodynamic analysis aimed to help physicians identify patients at high risk of cerebral hyperperfusion should account for the combined effect of the anatomy of cerebral arteries and cerebral feeding artery stenoses on cerebral hemodynamics.

/pdf/a-computational-model-study-of-the-influence-of-the-anatomy-4oiiezyk6r.pdf

A computational model study of the influence of the anatomy of the circle of willis on cerebral hyperperfusion following carotid artery surgery

BACKGROUND AND PURPOSE: Volume flow rates in the feeding arteries of the brain are measured to evaluate blood flow dynamics in vascular disease. Although these flow values are thought to be effected by anatomic variations in the circle of Willis, few reports have described the effect. This study reports on the relationship between variations in the circle of Willis and volume flow rates in the bilateral internal carotid and basilar arteries of normal volunteers. METHODS: We prospectively examined 125 healthy volunteers by MR imaging. Variations in the circle of Willis were classified as “textbook” type, hypoplasia of the precommunicating segment of the anterior cerebral artery (A1), hypoplasia of the precommunicating segment of the posterior cerebral artery (P1), or “other.” Volume flow rates were measured by 2D cine phase-contrast MR imaging. Lumen boundaries and volume flow rates were semiautomatically determined by pulsatility-based segmentation. RESULTS: Of the 117 subjects (61 men, 56 women; mean age, 23.6 years) considered suitable for flow measurement, 105 showed textbook type, and 6 each showed A1 hypoplasia and P1 hypoplasia. Total flow rates for the 3 variations were 781 ± 151 mL/min (mean ± SD), 744 ± 119, and 763 ± 129, respectively. Relative contributions by flow rates of the internal carotid arteries and the basilar artery for the 3 variations were 39.8%:38.9%:21.3%, 31.8%:49.1%:19.0%, and 46.6%:41.6%:11.7%, respectively, showing statistically significant differences. CONCLUSIONS: Variations in the circle of Willis correlate significantly with relative contributions by the flow rates of the bilateral internal carotid and basilar arteries.

http://www.ajnr.org/content/ajnr/27/8/1770.full.pdf

Relationship between variations in the circle of willis and flow rates in internal carotid and basilar arteries determined by means of magnetic resonance imaging with semiautomated lumen segmentation : Reference data from 125 healthy volunteers

Based on the indicator dilution theory, cerebral blood flow (CBF) can be quantified from dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) by deconvolution between the arterial input function (AIF) and the concentration curve in the brain [1]. There are several methods for performing deconvolution, and an algebraic approach based on singular value decomposition (SVD) has been shown to be one of the most reliable options. The purpose of this study was to investigate the effect of the threshold value for SVD on the accuracy of CBF quantification from DSC-MRI under various conditions.

Accuracy of cerebral blood flow obtained from dynamic susceptibility contrast-enhanced MRI using deconvolution analysis based on singular value decomposition

Cerebral blood flow (CBF) can be quantified using the brain perfusion index (BPI), determined from radionuclide angiographic data generated by 99mTc-HMPAO or 99mTc-ECD. The BPI is generally calculated using graphical analysis (GA). However, the BPI values obtained by GA (BPIG) are not in proportion to CBF. In this study, we measured BPI using spectral analysis (SA) (BPIS), and compared them with BPIG to investigate the carefulness of BPIS.

Development of a simple and non-invasive method for measuring cerebral blood flow using Technetium-99m compounds and spectral analysis

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Relationship between variations in the circle of willis and flow rates in internal carotid and basilar arteries determined by means of magnetic resonance imaging with semiautomated lumen segmentation : Reference data from 125 healthy volunteers

Accuracy of cerebral blood flow obtained from dynamic susceptibility contrast-enhanced MRI using deconvolution analysis based on singular value decomposition

Development of a simple and non-invasive method for measuring cerebral blood flow using Technetium-99m compounds and spectral analysis